The present invention relates to lane following vehicle control technique for controlling a vehicle along a lane of a road.
A Published Japanese Patent Application Kokai Publication No. 7(1995)-104850 discloses a driver assist system for controlling a steering torque for lane following.
This driver assist system is arranged to produce an automatic steering torque in accordance with input information on a lane, and to improve a lane following control performance by varying a control gain for multiplication of a deviation of a sensed steering angle from a required steering angle, in accordance with a vehicle speed and/or lateral acceleration.
The adjustment of the control gain based on vehicle speed and/or lateral acceleration is insufficient to prevent the course of the vehicle from deviating from an intended course in case of longitudinal load transfer due to hard acceleration/deceleration and changes in cornering force. A feedback control system based on image information obtained by a video camera functions to correct the deviation. During this correction, however, the vehicle tends to behave unsteadily.
When the lateral acceleration is estimated from the vehicle speed and steering angle, the control system is unable to steer the vehicle sufficiently along a curved road with a normal command in an accelerating state in which the cornering force is decreased from a desired level for a target steering angle, and the control system tends to cause the vehicle to turn too much in a decelerating state in which the cornering force is increased. If the control system is arranged to suspend the lane following control each time of acceleration/deceleration in such an unstable region, the value of the motor vehicle will become lower.
Moreover, squat during acceleration or dive during braking may divert the aiming direction of a camera from the desired direction, and deteriorate the accuracy of the lane detection.
It is therefore an object of the present invention to provide lane following vehicle control apparatus and/or process restraining unwanted changes in lane following control performance during acceleration or deceleration, and maintain stable running operation without providing unnatural feeling to a driver.
According to the present invention, a lane following vehicle control apparatus for a vehicle, comprises: a lane sensing section to collect information on a lane of a road ahead of the vehicle; a steering angle sensing section to sense an actual steering angle of the vehicle; a longitudinal acceleration sensing section to sense a longitudinal acceleration(or acceleration/deceleration) of the vehicle; a steering torque producing section to produce an actual steering torque in accordance with a target steering torque to follow the lane; a steering torque controlling section to set the target steering torque required for the vehicle to follow the lane, in accordance with the information on the lane and the actual steering angle; and a target steering torque limiting section to limit the target steering torque by setting a target torque limit in accordance with the longitudinal acceleration.
A lane following vehicle control process according to the present invention comprises: collecting input information on a vehicle running condition of a vehicle running along a lane, and an actual steering angle of the vehicle; obtaining a sensed actual longitudinal acceleration of the vehicle; producing a control signal to produce an actual steering torque in accordance with a target steering torque to follow the lane; setting the target steering torque to achieve a target steering angle determined in accordance with the vehicle running condition and the actual steering angle to follow the lane; and limiting the target steering torque by setting a target torque limit in accordance with the longitudinal acceleration.
A lane following vehicle control apparatus according to another aspect of the invention comprises: means for collecting input information on a vehicle running condition of a vehicle in relation to a lane; means for sensing an actual steering angle of the vehicle; means for sensing a longitudinal acceleration of the vehicle; means for producing an actual steering torque in accordance with a target steering torque to follow the lane; means for determining a target steering angle in accordance with the vehicle running condition and the actual steering angle to follow the lane; means for setting the target steering torque to achieve the target steering angle; and means for limiting the target steering torque by setting a target torque limit in accordance with the longitudinal acceleration.
The other objects and features of this invention will become understood from the following description with reference to the accompanying drawings.